This invention relates to novel compounds or compositions and methods of preparing same. The invention also relates to emulsifiers, especially to emulsifiers for use in explosive compositions, especially emulsion explosive compositions. The invention further relates to explosive compositions especially emulsion explosive compositions.
Emulsion explosives are in large scale commercial use around the world. They are made up of two inmiscible liquid phases in a stable emulsion. Usually such an emulsion comprises a discontinuous aqueous phase in a continuous lipid phase. The aqueous phase usually contains a high concentration of oxidiser salts such as ammonium, sodium or calcium nitrates. The lipid phase acts as a fuel and usually consists of selected petroleum products (oils). An emulsifier in the form of a surface-active chemical is required to form a stable, useful emulsion.
Emulsions are often made by mixing a hot concentrated solution of inorganic oxidiser salts in water, with a petroleum oil that has a suitable emulsifier dissolved in it. The resulting emulsions are technically unusual in that they are high internal-phase invert (xe2x80x9cwater-in-oilxe2x80x9d) emulsions, are very viscous, and the highly concentrated oxidiser salts in the disperse phase droplets should not crystallise out on cooling of the emulsion as one would expect. Durable, stable supersaturation occurs in these droplets. When crystallisation does occur, the explosive capability of the emulsion diminishes and is lost. This is a good fail-safe feature for old explosives but it is most undesirable in most commercial explosive products that need to be stored or kept for some period before actual use.
As is well known to those skilled in the art, a key to a good emulsion product is the emulsifier, which is a chemical whose molecules preferentially occupy the interface between the two phases thereby forming a barrier layer and preventing coalescence of the dispersed phase droplets. The emulsion is thus rendered stable.
During the 1970""s/1980""s the use of polyisobutenyl succinic anhydride (xe2x80x9cPIBSAxe2x80x9d) derivatives as superior emulsifiers for emulsion explosives was commenced with. The main classes of organic chemicals that will form an adduct with PIBSA are alcohols, polyols, amines and alkanolamines. Since the 1980""s emulsifiers in the form of the adduct of monoethanolamine or diethanolamine of PIBSA have been sold and exploited.
The inventor of the present invention has now prepared the adduct of PIBSA with urea. It was not expected that urea would react with PIBSA to form a material useful as an emulsifier in the preparation of emulsion explosives. Surprisingly it was found that this adduct showed superior performances as an emulsifier in emulsion explosives, compared to known products such as the adduct of monoethanolamine with PIBSA. A sample of an emulsion explosive composition containing the adduct of PIBSA and urea displayed a longer shelf life (slower crystallisation of oxidiser salts) than control samples made at the same time with the adduct of PIBSA and monoethanolamine. As far as the inventor is aware, last mentioned adduct has up to now given the best available shelf life.
It is accordingly one object of the present invention to provide an alternative emulsifier.
According to one aspect of the present invention there is provided an adduct of polyalk(en)yl succinic anhydride and a compound of formula: 
wherein
R1 is hydrogen, hydroxyl, hydrocarbyl, hydroxyhydrocarbyl, carbamyl, 1-acetyl, amino, or nitro;
R2 is hydrogen, hydroxyl, hydrocarbyl, hydroxyhydrocarbyl, carbamyl, 1-acetyl, amino, or nitro;
R3 is hydrogen or hydrocarbyl; and
X is O, S or NH ;
or a derivative of such an adduct.
When X is NH, then R1 and R3 are preferably hydrogen and R2 is preferably hydrogen or nitro. Preferably the compound of formula (I) is guanidine [NHxe2x95x90C(NH2)2] or nitroguanidine [NH2C (xe2x95x90NH)NH.NO2].
When X is S, then R1, R2 and R3 are preferably hydrogen. That is the compound thiourea [Sxe2x95x90C(NH2)2].
In a preferred embodiment of the invention X is O. R3 is preferably hydrogen. R1 is preferably hydrogen and R2 is preferably hydrogen, hydroxyl, hydrocarbyl, hydroxyhydrocarbyl, carbamyl, 1-acetyl or amino. Alternatively R1 and R2 both may be carbamyl.
Preferably, the hydrocarbyl of R1 and R2 is alkyl, preferably an alkyl with not more than 3 carbon atoms.
Preferably, the hydroxyhydrocarbyl of R1 and R2 is xe2x88x92ROH wherein R is an alkyl.
Preferably the compound of formula I comprises a compound selected from the group consisting of urea [H2NCONH2], hydroxyurea [HONHCONH2], methylurea [CH3NHCONH2], methylolurea [HOCH2NHCONH2], biuret [NH2CONHCONH2], triuret [NH2CONHCONHCONH2], and semicarbazide (or aminourea) [NH2CONHNH2].
Preferably the compound of formula I comprises urea.
The derivative of the adduct may comprise a heterocyclic condensate formed from the adduct where the adduct has an open acid-amide structure or it may comprise a hydrated acid formed from the adduct where the adduct is a heterocyclic condensate.
The polyalk(en)yl succinic anhydride preferably comprises polyisobutenyl succinic anhydride (PIBSA). The PIBSA may have a molecular weight from about 270 to about 2500. Preferably it is from about 950 to about 1200. In one preferred embodiment it is about 1000, and one such product is known in the trade as Lubrizol ADX 101B which has a molecular weight of about 1050.
Preferably the adduct is an adduct of polyalk(en)yl succinic anhydride and urea. Most preferably the adduct is an adduct of PIBSA and urea.
The compound of formula I and the polyalk(en)yl succinic anhydride may be reacted in a molar ratio from 0.5:1 to 1:1; preferably 0.5:1 to 0.75:1; most preferably 0.67:1.
Most preferably it comprises the adduct of urea and PIBSA wherein they have a molar ratio of 0.67:1.
The polyalk(en)yl succinic anhydride and compound of formula I may be reacted with each other at a temperature above 60xc2x0 C. and preferably below 140xc2x0 C., prefreably at a temperature from 80 to 120xc2x0 C., preferably 100 to 120xc2x0 C., most preferably at 120xc2x0 C. The reaction time will depend on the reaction temperature and may be from 1 hour (at higher temperatures) to 22 hours (at lower temperatures). Preferably the reaction is carried out at 120xc2x0 C. for 1 hour.
Without limiting the scope of the invention, it is believed that the adduct which forms when PIBSA reacts with urea is one or more of the following compounds: N-(carbamyl) polyisobutenylsuccinamic acid; its condensate N-(carbamyl)-3-polyisobutenyl-2,5-pyrrolidinedione; N,Nxe2x80x2-ketobis(polyisobutenyl-succinamic acid); and its condensate N,Nxe2x80x2-ketobis(3-polyisobutenyl-2,5-pyrrolidinedione). It is believed that the preferred adduct which forms is a mixture of the above compounds, and it is believed that the acids form the major portion of such a mixture. It is also believed that if the reaction is carried out a higher temperature for a longer period of time, an increasing amount of the heterocyclic condensates will form.
According to another aspect of the present invention there is provided an emulsifier comprising an adduct or derivative thereof substantially as described hereinabove. Preferably the emulsifier is suitable for use as an emulsifier for water and oil emulsions, preferably as an emulsifier in an emulsion explosive composition. According to another aspect of the present invention there is provided the use of an adduct or derivative thereof substantially as described hereinabove as an emulsifier.
According to another aspect of the present invention there is provided an emulsion including an emulsifier substantially as described hereinabove.
According to another aspect of the present invention there is provided an emulsion comprising a discontinuous liquid phase containing an oxygen supplying component; a continuous liquid phase of an organic medium; and an adduct or derivative thereof substantially as described hereinabove. Preferably the emulsion is an emulsion explosive composition.
The discontinuous phase may comprise an aqueous phase and preferably it comprises an oxidiser salt dissolved in water. The oxidiser salt may comprise a nitrate salt and preferably it comprises ammonium nitrate.
The organic medium may comprise a petroleum product, preferably an oil.
According to yet another aspect of the present invention there is provided an explosive composition comprising a mixture of a dry explosive or oxidising salt; and an emulsion explosive composition substantially as described hereinabove.
According to another aspect of the present invention there is provided a method of preparing a compound comprising reacting polyalk(en)yl succinic anhydride with a compound of formula I.
The compounds may be reacted with each other under heating. Preferably the products are stirred while heated above 60xc2x0 and preferably below 140xc2x0 C., preferably at a temperature from 80 to 120xc2x0 C., preferably 100 to 120xc2x0 C., most preferably at 120xc2x0 C. The reaction time will depend on the reaction temperature and may be from 1 hour (at higher temperatures) to 22 hours (at lower temperatures). Preferably the reaction is carried out at 120xc2x0 C. for 1 hour. Preferably the polyalk(en)yl succinic anhydride is preheated, preferably to about 40xc2x0 C.
The method may also include the step of forming a heterocyclic condensate of the adduct where the adduct includes an open acid-amide structure. Alternatively it may include the step of forming a hydrated acid of the adduct where the adduct includes a condensated acid.
The compound of formula I and the polyalk(en)yl succinic anhydride may be provided in a molar ratio from 0.5:1 to 1:1, preferably 0.5:1 to 0.75:1, most preferably 0.67:1.
The invention will now be further described by means of the following non-limiting examples.